Irretrievable loss of information stored in a computer system is highly undesirable. As a general matter, information is stored in a computer system in one or more files. To prevent loss of data, computer files are typically “backed up” periodically. Copies of computer files, i.e. backup files, are created and stored in a location separate from the file-generating computer systems. Such backup files allow recovery of information in the event of a system crash, natural disaster, or operator error that causes data stored on the system to be destroyed or lost.
One problem associated with backing up computer files is the speed of the process, i.e., the time required to create and write such a backup file. Often either the backup media or the connection between the computer system and the backup media is limited to data transfer rates which are substantially slower than the speed of the computer system on which the data is stored. For example, when backing up a host computer to a data storage device, such as a tape drive, over a network, the software orchestrating the creation and saving of the backup file, and the data transfer rate of the data storage device, are likely to be limiting factors in the overall speed of backup file creation and storage. Allocating substantial amounts of the host computer's time and resources to create and save backup files is undesirable.
Automated media storage libraries are known for providing cost effective access to large quantities of stored information, such as backup computer files. Generally, media storage libraries include a large number of storage slots on which are stored portable data storage media. The typical portable data storage media is a tape cartridge, an optical cartridge, a disk cartridge, electronic storage media, and the like. By electronic storage media, Applicants mean a device such as a PROM, EPROM, EEPROM, Flash PROM, and the like,
One (or more) accessors typically retrieve portable data storage media from the storage slots and deliver that accessed media to a data storage device for reading and/or writing data thereon. Suitable electronics operate the accessor(s) and operate the data storage device(s) to provide information to, and/or to receive information from, one or more attached host computer systems.
In a conventional automated media storage library, the storage slots are arranged in a planar orthogonal arrangement forming a “wall” of storage slots for holding data storage media. The plane may be a flat plane, or may be a cylindrical plane. To double the storage capacity, two “walls” of storage slots may be provided on either side of the accessor.
A number of different companies manufacture automated media storage libraries today, each model displaying various different features. One example is the IBM TotalStorage™ 3584 Enterprise Tape Library. Some of the automated media storage libraries have dual or multiple accessors to provide a level of redundancy and to enhance performance.
In order to most efficiently backup information stored on a host computer what is needed is a method employing time efficient copy protocols, i.e. fast software, in combination with a communication link having a high data transfer rate to a data storage device, where that method minimizes the overhead processing time required by the host computer, to create and save backup files on cost-effective data storage media.